In a general TDMA (Time Division Multiple Access) system (just like GSM, DECT), multiple time slots can be used at the same time to transfer data for enhancing the transmission rate; but the reflected data flow control would be more complex. For example, by the way of Sequence Number, receiver will recover the data by the sequence number of every data segment, so the overhead of data, buffer size, and operating speed should be limited.
FIG. 1 is a traditional DECT system. There are 24 time slots in one data frame: the first half is downlink (from FP (Fixed Part) to PP (Portable Part)), and the second half is uplink (from PP to FP). In general, a PP would create a single channel with an FP, for example, using the pair of (Slot 2, Slot 14) time slots. But for high data transmission purpose, we may create N channels between a PP and a FP; that is, we may enhance the transmission rate via using 2N time slots concurrently. So, the data of FP will be partitioned into several units by the base of a time slot's size, and be transferred via N channels sequentially; and so does PP. But the flow control would become more and more difficult.
FIG. 2 shows a traditional multi channels transmission from a FP to a PP. If there are 5 channels existed in one data frame concurrently, then the data transmission rate will be enhanced by 5 times. But if channel 1, 3, 5 transfer data successfully and channel 2 and 4 don't, then how can a PP manage the received data segments is a very important topic.
U.S. Pat. No. 6,021,124 provides a similar solution: pushing data segments into every channel's FIFO (First In, First Out) stack and transferred by every channel respectively. For example, there are 10 data segments numbered by 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, and there are 5 channels for data transferred; the arrangements are: Channel 1 transfers segment 0 and 5, Channel 12 transfers segment 1 and 6, Channel 3 transfers segment 2 and 7, Channel 4 transfers segment 3 and 8, and Channel 5 transfers segment 4 and 9. If Channel 2 fails, then segment 6 cannot be transferred until segment 1 transferred completely; but if segment 1 always cannot be transferred, then all the data queued in Channel 2 cannot be transferred to receipt end. This will affect the data transmission rate.